The visit by Federal Reserve examiners was made around the same time as, prosecutors alleged, a woman in Seattle was trying to access a Capital One Financial Corp <COF.N> database stored on Amazon's cloud server, the Journal reported https://on.wsj.com/334v73h.

The authorities examined Amazon's resiliency and backup systems and described their visit as the first in their ongoing oversight of the company, the report added.

Several U.S. lawmakers had previously called for oversight of big tech companies such as Amazon, expressing a growing concern about the size of the largest tech firms and their market power.

The authorities were allowed to review some documents on Amazon laptops but were not allowed to take anything with them, according to the report, which added that Fed officials were not aware of the Capital One data breach under way at the time.

Amazon did not immediately respond to a request for comment on Thursday.

Capital One said earlier this week that 106 million people who had applied for credit cards in the United States and Canada had their personal data exposed.

The breach, which occurred between March 12 and July 17, stemmed from Capital One's decision to store data in Amazon's cloud unit, called Amazon Web Services (AWS), where a former employee named Paige Thompson managed to access its data.

She was charged with computer fraud by federal prosecutors in Seattle.